The present invention relates to a composition suitable for application to metal products for marking or antiscaling purposes, and to methods of making and using the composition, respectively.
There is an urgent need in the steel industry for marking inks which can be used to identify hot slabs and billets and will withstand surface temperatures exceeding 1600.degree. F. Inks currently used bubble badly when applied on surfaces which are above 1600.degree. F. and do not adhere when the surfaces cool to ambient temperatures. The composition of an ink currently used is disclosed in U.S. Pat. No. 3,640,737, Lankard and Sheets, Jr. of common ownership with the present application. U.S. Pat. No. 3,732,115, a division of the aforementioned patent and also of common ownership, covers the method of making this composition. The compositions disclosed in these references will not work much above 1600.degree. F. and certainly not at 2000.degree. F. which is of immediate interest for making hot steel mill products.
Applicant is not aware of any prior art suggesting use of borates to improve the high temperature properties of marking compositions and permit their use on metal products having surface temperatures above 1600.degree. F. Borax is known to act as a chemical setting agent in alkali metal silicate systems. Because of its setting characteristics, borax is confined to use as an aftertreatment for improving moisture resistance of the silicate bond. Small amounts of borax may be used in coatings curable at room temperature to provide excellent water resistance. U.S. Pat. No. 4,169,735, Boberski et al teaches that from 0.1 to 5.0 percent of borate latent insolubilizers may be used in alkali metal silicate coatings based upon the combined weight of water-soluble silicate and borate latent insolubilizers. Example 6 of Boberski et al discloses the highest percentage of borate insolubilizer actually tested ##EQU1## Relative to applicant's claimed composition the B.sub.2 O.sub.3 equivalent 0.365 (6.75 g)=2.46 g B.sub.2 O.sub.3 amounts to 0.78% of the total solids of Example 6. On the same basis, applicant's composition requires at least 1.5% B.sub.2 O.sub.3 to obtain the desired high temperature properties for marking compositions. Moreover, applicant's composition is also distinguishable in that at least 50 percent of the alkali metal silicate must be sodium silicate. Finally, applicant's composition must be baked at temperatures of at least 250.degree. F. whereas the Boberski composition is curable at room temperature.
It is therefore a primary object of the present invention to provide a composition suitable for application to metal products having temperatures significantly above 1600.degree. F. for purposes of producing legible markings thereon.
It is another object of the present invention to provide a method of making such a composition.
It is a further object of the invention to provide a composition suitable for application as a coating on metal products to resist or prevent scaling of the metal surface during heating.